Would 4ns rated SDRAM running at max of 240MHz aiding your comprehension?
Uhhh...no. And I wouldn't get testy about it.
<< find... how many or who will supply 200MHz SDRAM >>
...
Simplified, does that help?
Uhhh...no again. At the risk of prolonging this, what EXACTLY are you asking?
1) As was posted above, SDRAM that will run at least at 200MHz is supplied by Samsung (5ns, look at any Kyro II board) and EtronTech (3.5ns good for a real world 260MHz in the THG review noted by Mingon).
2) Above on videocards above 200MHz, SDRAM usually gets dumped in favor of DDR for bandwidth reasons anyways. The only "performance" videocard using SDRAM ("performance" defined as competitive framerates at or above 1024x768x32) is the Kyro, and that's because of its tile-based architecture. No other SDRAM card - GeForce2 MX, Radeon SDR - is in the same league. Even with 260MHz SDRAM, the Gainward MX400 gets wasted by a GeForce2 GTS with 166MHz DDR at 1024x768 and higher resolutions. You'll note that the Kyro 3 will support both DDR and SDR, so if it's clocked as rumored at 250MHz, there's no problem finding memory for either version.
As for the Kyro 2 Ultra rumors, it'll be clocked at 200MHz, which means the Samsung 5ns SDRAM will work fine.
3) What's the relevance of DIMM modules in a discussion about video card memory? No consumer card I'm aware of uses DIMM modules. Fastest SDRAM I've heard of on a DIMM is 6ns.